Limiting power consumption by a computer processor has several benefits including: reducing energy costs, reducing heat build-up and the burden on a cooling system to remove heat dissipated by the processor, and, in the case of a battery-powered computer, extending battery life. Accordingly, many processors have different power states, including performance states and idle states. The different performance states can involve different clock frequencies, with higher clock frequencies providing higher performance, but consuming more power. The idle states can include, for example, “power off”, “hibernate”, and “sleep states”.